Modern scanning receivers typically comprise a wide band receiver with phase lock loop frequency synthesis and a microcontroller having a memory. Various operational controls and data are entered using a key matrix keypad and conventional controls, such as an audio volume potentiometer and squelch threshold potentiometer. Also, a display is typically included to display frequency and channel information together with other operational status indicators. The memory is commonly divided into various portions which may include ROM for permanent storage of the executable code embodying the various functions of the receiver, RAM for storage of temporary variable and such, and, EEPROM for non-volatile storage of user programmed information such as frequency and channel information, and power-on configuration information.
The portion of memory used to store frequency information is commonly referred to as a channel memory because each of a plurality of storage locations stores a number corresponding to a unique frequency, and this frequency is referenced as a channel. The reason for the correspondence of a particular storage location or channel to a programmed frequency is to simplify the memorization of what kinds of radio communications are available by recalling the number corresponding to a particular frequency from a particular channel memory storage location. For example, a user may have programmed a frequency, 110.000 megahertz in the aircraft band, into channel one in the channel memory in a receiver. Thereafter, when the user desires to listen to the aircraft band, all the he need do is recall channel one. Actually, to store 110.000 megahertz in the channel memory, the microcontroller would have stored a frequency divisor at channel memory storage location one. When memory location one, (channel one), is subsequently recalled, the microcontroller recalls the divisor stored therein and loads the divisor into a phase lock loop synthesizer where it is used to generate a beat frequency, in a first local oscillator, needed to receive the desired frequency of 110.000 megahertz.
The foregoing example recited just one frequency, however most radio services comprise a large number of frequencies. For example, the aircraft band comprises all the frequencies from approximately 108 megahertz to 137 megahertz. In any particular geographic area, several of these frequencies will likely carry intermittent signals. Therefore, it is common for the user to group a plurality of channels together in the channel memory so that they can be scanned by the receiver, increasing the probability that the receiver will receive an active signal frequency in the particular frequency band of interest to the user. Additionally, a particular user may be interested in several different service bands, such as police, emergency medical, fire, government, and etc.
Scanning receivers arrange the channel memory into banks of storage locations, or channels. This is done so that the user can activate one or more channels banks at the time scanning is initiated. Particular banks may be activated based on what kinds of radio services are programmed therein, or, how many channels can be effectively scanned at one time.
The process of programming the channel memory is time consuming and prone to errors and confusion. Upon discovering or learning of a particular frequency of interest, the user selects a channel memory storage location, or channel, and enters the desired frequency in megahertz. For example, the frequency 110.265 megahertz is entered by keying in the digits "1", "1", "0", ".", "2", "6", "5", and then entering the frequency with another key stroke. Each new frequency is entered in turn until all of the frequencies of interest have been stored. If the user is interested in several different radio service bands, each frequency for each service must be entered.
The scanning receiver scans a contiguous group of channels or channel banks. Therefore, it is necessary to program the channels in such a sequence as to allow the desired group of frequencies to be scanned as a contiguous group of channels. Since the various frequencies are sometimes discovered or learned over a long period of time, or, new frequencies become active from time to time, it is often necessary for the user to rearrange the channels in order to keep certain desired groups of frequencies together in a contiguous block of channels. This process involves numerous keystrokes and is prone to error. Also, it is possible for the user to inadvertently overwrite a desired frequency in the channel memory while moving another frequency into a new channel location.
It is therefore necessary and desirable to invent a method wherein the foregoing problems are solved and the management of a plurality of frequencies in a channel memory is simplified and the number of keystrokes required to affect the desired changes is minimized. Furthermore, the management of banks of channels and full versus clear storage locations needs to be improved and simplified.